It looks like we might have a connection here.
I have an Unknown Jones living in Llawdre prior to 1805. Perhaps this is your David Jones (1792- 1865).
Unknown Jones had 2 daughters that I know of:
Sarah Jones (b. 1805), married John Protheroe (from Tymawr) on June 2, 1832 in Llanwrtyd.
Mary Jones (b. ?), married Rees Protheroe (from Tymawr) on June 6, 1832 in Llanwrtyd. The 1881 census shows Rees Protheroe living in Troedrhiwfallan. From there ... a dead end!
Sarah was my direct ancestor and I have an extensive (but perhaps not quite complete) genealogy of her descendents to this day.
William Protheroe (a third son from Tymawr) b. 1813, m. abt 1837 to Elizabeth Jones (from Pwllbo) were living in Tymawr in 1861 and 1881, and I have an extensive genealogy of this line also.
I have too much info to put on this bulletin board. Please reply by email.